The present invention relates to a read-only sequence controller, and more particularly to a sequence controller having a control unit with an output relay unit detachably attached thereto.
A conventional sequence controller has a source unit, sequential control unit, and output relay unit responsive to output signals of the control unit for producing output signals for sequentially operating machines. These units are arranged side by side so that the area of the sequence controller becomes very large. Accordingly, such a controller is not suitable to be attached to a machine to be controlled.